Gas evolving oil viscosity diminishing compositions for stimulating the productive layer of an oil reservoir

ABSTRACT

Disclosed is a chemical system of gas evolving oil viscosity diminishing compositions (GEOVDC) for stimulating the productive layer of an oil reservoir, that is to chemical compositions for a thermochemical treatment of an oil reservoir, more specifically for initiating a chemical reaction in the productive layer zone of the oil reservoir to produce heat and evolve gases so that the extraction of oil (petroleum) is improved. Further disclosed is a method of thermochemically treating an oil reservoir by means of this chemical system, and an apparatus for performing thermochemical treatment of an oil reservoir.

CROSS-REFERENCES

This application is a Continuation of U.S. patent application Ser. No.13/124,637, filed Apr. 15, 2011, claiming priority under 35 U.S.C. 371from International Patent Application No. PCT/EP2008/008725 filed Oct.15, 2008, the entire contents of which are herein incorporated byreference.

BACKGROUND OF THE INVENTION

The invention is directed to a chemical system of gas evolving oilviscosity diminishing compositions (GEOVDC) for stimulating theproductive layer of an oil reservoir, that is to chemical compositionsfor a thermochemical treatment of an oil reservoir, more specificallyfor initiating a chemical reaction in the productive layer zone of theoil reservoir to produce heat and evolve gases so that the extraction ofoil (petroleum) is improved. The invention is further directed to amethod of thermochemically treating an oil reservoir by means of thischemical system, and to an apparatus for performing thermochemicaltreatment of an oil reservoir.

The extraction of petroleum from an oil reservoir usually starts withrecovery methods using underground pressure in the oil reservoir whichwill force the oil to the surface. Over the lifetime of the oil well thepressure decreases, and it becomes necessary to use other extractionmethods such as using pumps or injecting water, natural gas or othergases into the oil well to bring the oil to the surface. After recoverymethods are no longer effective the oil reservoir usually still containsconsiderable amounts of petroleum being enclosed in small cavities orpores of the rock or sand formations.

To recover the remaining amounts of petroleum tertiary oil recoverymethods are used which mainly have the aim to reduce the viscosity ofthe petroleum. One common method is to inject hot steam into the oilwell to heat the petroleum and thus to reduce its viscosity. Thismethod, however, is efficient only up to a depth of about 1 km asotherwise the hot steam will be cooled down before reaching the payzone. Further, with this method up to 3 to 5 months of injecting hotsteam are necessary to heat up the pay zone. Alternatively, surfactantsor solvents can be injected into the oil well to leach out thepetroleum. Such methods however, have the disadvantages that theextracted petroleum will be contaminated by chemicals so that additionalefforts and costs are necessary to recover the petroleum.

Another tertiary oil recovery method is characterized in that a chemicalreaction is initiated in the pay zone of the oil reservoir to producehot gases which heat up the oil in the pay zone to reduce its viscosityand to support oil recovery by increasing the pressure in the oil well.

Disclosed in Russian patent applications RU 2100583 C1, RU 2126084 C1and RU 2153065 C1 are fuel and oxidizing compositions (FOC) which areable to produce hot gases after initiating a chemical reaction. FOC areintended to be introduced into the oil well of an oil reservoir for athermochemical treatment of the pay zone. The chemical compositions areaqueous solutions containing large amounts of up to 60% by mass or moreof ammonium nitrate, NH₄NO₃. The other components of FOC are forinstance glycerin, nitric acid, carbamide, potassium permanganate,acetic acid, isopropyl metacarborane and acetylsalicylate. Afterinjection of the FOC into the oil well it is ignited by initiating afuse explosion. The decomposition of 1 kg of FOC results in emitting aquantity of heat of about 500-1000 kcal.

FOC contain an excess of oxygen and hence have a substantial oxidizingcharacter, so that with the admixture of petroleum an explosivecomposition is created. Further, aqueous solutions containing largeamounts of ammonium nitrate are explosive if the water content is belowa critical amount of about 16-18% by mass. Hence, in view of safehandling of such compositions the water content is usually above 26-28%by mass. However, with increasing water content it becomes more and moredifficult to achieve a stable reaction with a high output of heat.

In Russian patent application RU 2194156 C1 the FOC contains mainly thereaction product of nitric acid with an alkanolamine, alkyl amine oralkyl polyamine and up to 2.0 to 35.0% by mass of an inorganic nitratesuch as ammonium nitrate, potassium nitrate, sodium nitrate or calciumnitrate. With such a composition safer handling was achieved as theamount of ammonium nitrate could be reduced substantially. However, withthe usual way of igniting the FOC by means of a fuse explosion, forsafety reasons a maximum mass of only 1 to 2 tons can be ignited. Afterdecomposition of the FOC feed with a mass of 1 to 2 tons the wholeoperation of the FOC delivery and initiating charge insertion has to berepeated so that at an oil well with a depth of 1 to 2 km not more thanabout 10 tons of FOC can be reacted per day. If the oil well depth isabout 3 to 4 km the amount of FOC to be reacted per day with this methoddecreases to about 5 tons. Hence, the extent of heating the pay zone andthus the efficacy of this method is limited.

It is therefore the object of the present invention to provide improvedmaterials and an improved method to overcome the limitations of theprior art by considerably increasing the amount of heat generated in thepay zone of an oil well and thus allowing a profitable exploration ofoil reservoirs. A further object of the present invention is to providean apparatus for performing thermochemical treatment of an oilreservoir.

SUMMARY OF THE INVENTION

The above object is solved by providing a chemical system for thermallytreating an oil reservoir by initiating a chemical reaction in a payzone of the oil reservoir, wherein the chemical system comprises atleast the following two compositions:

-   -   a thermal gas emitting composition (TGEC) being an aqueous        solution or suspension comprising at least one compound selected        from the group consisting of hydrazine nitrate, 1,1-di C₂₋₆        alkyl hydrazine nitrates and 1,2-di C₂₋₆ alkyl hydrazine        nitrates, such as 1,1-dimethyl hydrazine nitrate or 1,2-dimethyl        hydrazine nitrate, guanidine nitrate, formamide nitric acid        adduct, acetamide nitric acid adduct, acetonitrile nitric acid        adduct, urea nitric acid adduct, ammonium nitrate, potassium        nitrate, sodium nitrate, calcium nitrate, mono, di and tri C₁₋₅        alkyl amine nitrates, mono, di and tri C₁₋₅ alkanol amine        nitrates, C₂₋₆ alkylene diamine mono and dinitrates and poly        C₁₋₅ alkylene polyamine polynitrates; and    -   a reaction initiator stabilizer (RIS) being a liquid and        comprising at least one compound selected from the group        consisting of:        -   metal borohydrides MBH₄, wherein M is Li, Na or K;        -   aminoboranes (R¹R²R³)N.BH₃, wherein R¹, R² and R³ are            independently hydrogen or C₁₋₁₀ alkyl, or wherein R¹ is an            aryl or pyridine with up to 10 carbon atoms and R² and R³            are hydrogen;        -   dialkylaluminates MAlH₂R¹R², wherein M is Li, Na or K, and            R¹ and R² are independently C₁₋₁₀ alkyl;        -   aminoalanes (R¹R²R³)N.AlH₃, wherein R¹, R² and R³ are            independently hydrogen or C₁₋₁₀ alkyl; and        -   aluminum or aluminum alloys with magnesium.

In the present invention two different compositions are used to initiatechemical reactions in the oil reservoir, especially in the pay zone ofthe oil well. The two compositions are introduced separately into theoil well such that they come into contact at the point where thechemical reaction should take place. These reactions are mainlyexothermic reactions producing large amounts of heat and gasesincreasing the temperature of the petroleum such that the viscosity ofthe petroleum is reduced and its extraction is improved. As a furtherresult of the reactions the pressure in the pay zone increases so thatthe recovery of the petroleum is supported. Moreover, the increasedpressure creates fractures in the formation so that recovery of thepetroleum is further supported.

The first composition is designated as a “thermal gas emittingcomposition (TGEC)” and contains the main quantity of the chemicalcompounds producing hot gases after a chemical reaction is initiated.The second composition is designated as a “reaction initiator stabilizer(RIS)” and has the function of initiating and maintaining the heat andgas producing reaction(s). The TGEC and the RIS are both liquids whichcan be introduced into the oil reservoir by means of pumps. If the usedcompounds are not liquid as such they are used as solutions orsuspensions in an appropriate solvent. If the TGEC and the RIS aresuspensions their viscosity is such that they still are pumpable and canbe pumped into the oil well with a rate of up to 4-8 liters per second.

Specific examples of compounds which can be used for the TGEC are mono-,di- and triethanolamine nitrates, mono-, di- and triethylamine nitrates,polyethylene polyamine polynitrates, ethylene diamine mononitrate,ethylene diamine dinitrate, alkylidene diamine mono- and dinitrates.

For the TGEC it is preferred to use an aqueous solution or suspensioncomprising at least one compound selected from the group consisting ofhydrazine nitrate, 1,1-di C₂₋₆ alkyl hydrazine nitrates and 1,2-di C₂₋₆alkyl hydrazine nitrates, such as 1,1-dimethyl hydrazine nitrate or1,2-dimethyl hydrazine nitrate, guanidine nitrate, formamide nitric acidadduct, acetamide nitric acid adduct, urea nitric acid adduct andacetonitrile nitric acid adduct.

The TGEC is preferably the reaction product of reacting nitric acid withthe respective amino compounds like reacting hydrazine with nitric acidsuch that hydrazine nitrate is obtained. By reacting nitric acid withthese amino compounds the respective nitrate compounds or nitric acidadducts are obtained.

If the TGEC contains one or more of ammonium nitrate, potassium nitrate,sodium nitrate or calcium nitrate these nitrates are contained in theTGEC with not more than 50% by mass, preferably not more than 30% bymass.

The pH value of the TGEC is preferably about 3 to 14 depending on theRIS and TGEC compositions. It is further preferred that the mixture ofTGEC and RIS has a pH value <7.

For the above mentioned aminoboranes, dialkylaluminates and aminoalanesit is preferred that the alkyl moieties R¹, R² and R³ are methyl orethyl.

If aluminum or an aluminum alloy with magnesium is used for the RIS thealuminum or aluminum alloy can be used as a fine dispersed, pyrophoricmaterial preferably having a particle size of about 1 μm or less and/orin the form of granules preferably having a particle size of about 0.1to 5 mm, more preferably 1 to 2 mm.

If the temperature in the oil well has reached about 250-300° C. asuspension of such granular aluminum or aluminum alloy with magnesium inan organic solvent can be introduced into the oil well.

The aluminum is oxidized in an exothermic reaction to give aluminumoxide wherein 5 kg of Al produce a thermal energy of about 50,000 Kcal.For example, to increase the temperature of 1 kg of the productive layerformation by 100° C. a thermal energy of about 20 Kcal is to beprovided, wherein increasing the temperature of 1 kg of petroleum by100° C. requires a thermal energy of about 50 Kcal.

The oxidation of aluminum results in formation of aluminum oxideparticles which deposits in the fractures formed in the pay zone to holdthem open so that oil extraction is further improved.

For preparing the solution or suspension of the RIS any appropriatesolvent may be used. In dependence of the materials used as the RIS suchappropriate solvent may be water or an organic solvent selected from thegroup consisting of petrol, ligroin, white spirit, kerosene and naphtha.If, for instance, metal borohydrides or aminoboranes are used for theRIS water with a pH value >7 can be used as a solvent. For achievingsuch pH value ammonia or an alkali metal hydroxide can be added. If amaterial is used which reacts with water one or more of the aboveorganic solvents may be used.

At the beginning of a thermochemical treatment of an oil well RIS isusually used with about 5-7% by mass with respect to the mass of TGECinjected into the oil well. After the chemical reactions are initiatedit is sufficient to use about 1% by mass of RIS with respect to the massof TGEC. With the chemical system of the present invention it ispossible to react up to several hundred tons of material per day in thepay zone of an oil reservoir, being about 50-100 times the amount ofmaterial which can be reacted per day with the systems and methods knownthus far. This can be achieved by continuously pumping the TGEC into theoil well and by separately pumping the RIS into the oil well, whereinthe RIS can be pumped continuously or intermittently. In case thetemperature at the place of reaction is in or above the range of about200-300° C. the introduction of the RIS can be interrupted as at suchtemperatures the TGEC will react stably and without an additionalignition. Below about 180-200° C. the injection of RIS must be resumed.

In contrast to the FOC used in the prior art, the TGEC of the presentinvention does not contain an excess of oxygen and thus has no oxidizingcharacter so that no explosive composition is created with the admixtureof petroleum. The decomposition of 1 kg of TGEC results in emitting aquantity of heat of about 1000-3200 kcal.

With the chemical system of the present invention it is possible toproduce more heat per time and thus to improve efficiency of the oilrecovery process as it is the first time that a stable and continuousreaction can be maintained by continuously pumping reactive materialsinto an oil well. Until now it was the general opinion that it is notpossible to initiate and maintain a stable and continuous reaction ofsuch huge amounts of reactive materials in an oil well. With GEOVDC ofthe present invention it becomes further possible to recover petroleumalso from oil reservoirs containing mainly high viscous petroleum whichcould not be efficiently recovered with the methods known thus far.

In a preferred embodiment of the present invention the RIS or TGEC canadditionally contain one or more soluble metal salts of Mn, Fe, Cr, Co,Ni or V. These metals are able to catalyze an oxidation of thepetroleum, so that additional heat can be produced. These metal saltsare contained in the RIS in an amount of not more than 10% by mass withrespect to the total mass of the RIS.

Especially preferred metal salts are Fe(NO₃)₃, Mn(NO₃)₂.6H₂O,Mn(SO₄).6H₂O, KMnO₄, K₂MnO₄, K₂CrO₄, Na₂CrO₄, K₂Cr₂O₇, Na₂Cr₂O₇,Co(NO₃)₃, NH₄VO₃, NaVO₃ and KVO₃.

The following is an overview of preferred ratios of the componentscontained in the GEOVDC comprising the TGEC and RIS wherein the ratiosare expressed as % by mass related to the combined mass of reagentscontained in the TGEC and RIS, yet without the solvents used forpreparing the respective solutions or suspensions.

TABLE 1 The TGEC compounds: 1. hydrazine nitrate 30-70% by mass  2.1,1-di C₂₋₆ alkyl hydrazine nitrates and 1,2-di C₂₋₆ alkyl hydrazinenitrates, such as 1,1-dimethyl hydrazine nitrate or 1,2-dimethylhydrazine nitrate 3. guanidine nitrate 4. formamide nitric acid adduct5. acetamide nitric acid adduct 6. acetonitrile nitric acid adduct 7.urea nitric acid adduct The TGEC compounds: 1. Mono-, di- andtriethanolamine nitrates if present at least 2. Mono-, di- and tri C₁₋₅alkyl amine 10% by mass nitrates, such as Mono-, di- and tri- ethylaminenitrates 3. Polyethylene-polyamine polynitrate 4. C₁₋₅ alkylidenediamine mono- and dinitrate, such as Ethylenediamine mononitrate orEthylenediamine dinitrate The RIS compounds: 1. metal borohydrides MBH₄1-10% by mass 2. aminoboranes (R¹R²R³)N•BH₃ 0.5-5% by mass  3.dialkyialuminates MAIH₂R¹R² 1.5-7% by mass  4. aminoalanes(R¹R²R³)N•AlH₃ 3-10% by mass 5. aluminum or aluminum alloys with 0.3-70%by mass   magnesium. Soluble salts of Mn, Fe, Cr, Co, Ni or V  1-4% bymass Ammonium nitrate, potassium nitrate, 0-50% by mass sodium nitrate,calcium nitrate

The method according to the present invention for increasing the amountof heat generated in the pay zone of an oil well and thus allowing aprofitable exploration of oil reservoirs is characterized in that theabove described chemical system is used wherein the thermal gas emittingcomposition (TGEC) and the reaction initiator stabilizer (RIS) areseparately introduced into the oil reservoir and are contacted in thepay zone of the oil reservoir to initiate a chemical reaction producingheat and gases.

It is preferred to introduce the TGEC continuously into the oilreservoir and to introduce the RIS simultaneously with the TGEC and in acontinuous or intermittent way.

With the method of the present invention the TGEC and RIS can be pumpedinto the oil reservoir with a rate of about 4-8 liters per second.

A specific embodiment of the method according to the present inventioncomprises the steps of:

-   a) introducing granules of aluminum or an aluminum/magnesium alloy    as the RIS into an oil well of the oil reservoir and keeping the    granules in a reaction chamber located in the oil well;-   b) introducing the TGEC into the oil well so that it contacts the    granules kept in the reaction chamber for initiating and maintaining    a thermochemical reaction producing heat and gases;-   c) passing the produced hot gases into the pay zone of the oil    reservoir;-   d) shifting the thermochemical reaction into the pay zone of the oil    reservoir by allowing the granules to enter into the pay zone; and-   e) contacting the granules in the pay zone with the TGEC introduced    into the oil well.

In the above method the reaction chamber is located in or adjacent tothe pay zone of the oil reservoir. The exact location of the reactionchamber depends on the construction of the apparatus used and of theconstruction of the oil well. Practically, the reaction chamber mayextend up to 500-600 m above the pay zone and may even extend severalmeters to several tens of meters below the pay zone.

A preferred TGEC compound for reacting with the granules of aluminum oraluminum/magnesium alloy is urea nitric acid adduct, the reactionproduct of urea with nitric acid.

The pH value in the reaction chamber is in the range of pH 3-14, whereina pH of about 3-4 is preferred as then the hydrogen gas produced by thethermochemical reaction is oxidized to H₂O so that the amount ofproduced heat is increased by about 30%.

In the step of shifting the thermochemical reaction into the pay zonethe thermochemical reaction and thus the granules are shifted intofractures present in the pay zone. This allows a direct heating of thesurrounding of the fractures so that the fractures can be increased withrespect to their length and volume.

This step of shifting the thermochemical reaction into the pay zone ispreferably carried out when the pay zone is heated up to about 300° C.

The method according to the present invention may further comprise astep of contacting the granules in the pay zone with at least one strongoxidizing agent such as potassium dichromate K₂Cr₂O₇. These strongoxidizing agents support the production of large amounts of energy andof solid metal oxides like Al₂O₃ which function as proppants (proppingagents) to hold the fractures open.

When sufficient high temperature and pressure are reached in the payzone and hydrogen is present as a result of the reaction of the aluminumor aluminum/magnesium alloy with the TGEC the petroleum in the oilreservoir is subjected to a hydrocracking process.

With hydrocracking the viscosity of the petroleum in the treated oilreservoir is considerably reduced as in addition to the increasedtemperature in the pay zone the more complex hydrocarbon molecules arebroken down to simpler hydrocarbon molecules.

The hydrocracking process may be further supported by adding suitablemetal catalysts such as metal salts of Mn, Fe, Cr, Co, Ni or V.

A large number of oil wells, especially older oil wells, arecontaminated or damaged by water contents. With the method of thepresent invention using aluminum or aluminum/magnesium alloys the amountof water present in the oil well can be reduced. During reaction of thealuminum or aluminum/magnesium alloys under alkaline conditions water isconsumed. Further, the metal hydroxides resulting from the reaction ofaluminum or aluminum/magnesium alloys have the characteristic ofadsorbing or bonding water like in the form of water of crystallization.

It is also possible to achieve a thermal cracking of the petroleum byfurther increasing the temperature in the pay zone. However, the processof hydrocracking as described above is preferred as it is more effectiveand it reduces the amount of water present in the pay zone.

The hydrocracking process in the pay zone of an oil well has never beendescribed before. It is a very effective method of a thermochemicaltreatment of an oil reservoir and thus allows profitable exploration ofoil reservoirs.

In another specific embodiment of the method according to the presentinvention the TGEC and RIS are introduced in the form of fluid layersseparated by layers of a spacer fluid. With this method it becomespossible to introduce the TGEC and RIS into the oil well through onetube and still achieve a separate but continuous supply of TGEC and RIS.

A further embodiment of the method according to the present inventioncomprises the steps of:

-   a) introducing granules of aluminum or an aluminum/magnesium alloy    as the RIS into an oil well of the oil reservoir and keeping the    granules in a first reaction chamber located in the oil well;-   b) introducing a first TGEC into the oil well so that it contacts    the granules kept in the first reaction chamber for initiating and    maintaining a thermochemical reaction producing thermal energy and    heating up the walls of the first reaction chamber;-   c) introducing a second TGEC into the oil well such that it comes in    contact with the heated walls of the first reaction chamber and is    ignited;-   d) passing the ignited TGEC to a second reaction chamber where the    TGEC reacts under production of heat and gases; and-   e) passing the produced hot gases into the pay zone of the oil    reservoir.

In this specific embodiment an apparatus may be used comprising aheat-resistant beaker with a perforated bottom at the lower end of atubing inserted into the oil well, so that the RIS granules will be keptin the beaker and can be contacted with the first TGEC introduced in thetubing. The section of the tubing with the attached beaker forms thefirst reaction chamber and will be heated by the thermochemicalreaction. The second TGEC will be passed along the outside of thistubing section and thus will be heated to a temperature sufficientlyhigh to induce ignition of the second TGEC.

In this method the beaker should be of such resistance that itwithstands the chemical and thermal conditions during the thermochemicaltreatment. In contrast thereto, if the above method further comprises ashifting of the thermochemical reaction into the pay zone this beakermay be fabricated of a material which gradually disintegrates under thechemical and thermal conditions. Such material may be aluminum or analuminum/magnesium alloy, for instance, which will react with the TGECprovided to the beaker or which will burn down at high temperatures.

The apparatus for performing thermochemical treatment of an oilreservoir according to the present invention allow separate introductionof the thermal gas emitting composition (TGEC) and the reactioninitiator stabilizer (RIS) described above and the contacting of theTGEC and RIS in or near the pay zone of the oil well to be treated. Suchapparatus comprise:

-   -   an outer tubing inserted in a casing of the oil well such that        an outer annular space between the outside of the outer tubing        and the inside of the casing is provided, wherein the lower end        of the outer tubing is located in or above the pay zone of the        oil well;    -   a packer being positioned above the lower end of the outer        tubing and sealing the outer annular space;    -   an inner tubing inserted in the outer tubing, such that an inner        annular space between the outside of the inner tubing and the        inside of the outer tubing is provided, wherein the inner tubing        allows the supply of one of the TGEC or RIS to the pay zone and        the inner annular space allows the supply of the other one of        the TGEC or RIS to the pay zone, and wherein the lower end of        the inner tubing is located in or above the pay zone;    -   wherein at least one of the lower end of the outer tubing and        the lower end of the inner tubing is located in the pay zone of        the oil well; and    -   a mixing device contacting the TGEC and the RIS in the pay zone        of the oil well.

The mixing device of such apparatus can be embodied by a sealed lowerend of the outer tubing being located above the lower end of the innertubing but below the packer; and openings in the inner tubing allowing afluid exchange between the inner annular space and the inner tubing,wherein the openings are located at a distal section of the inner tubingbut above the lower end of the outer tubing.

The openings are preferably embodied as slot jet nozzles having tubularconnecting passages extending diagonal through the inner tubing andcomprising a slot.

The slots are preferably formed in a lower half of the tubularconnecting passages.

In a specific embodiment of such apparatus a beaker is inserted in theinner tubing below the openings in this tubing, wherein this beakercomprises openings in its bottom allowing the passage of the mixedfluids but not of granular material supplied with the RIS through theinner tubing. That is, the openings in the bottom have a smallerdiameter than the granules supplied with the RIS.

The beaker can be made of aluminum or an aluminum/magnesium alloy if itis intended that the beaker has a limited lifetime during thethermochemical treatment so that after a predetermined time the granulesare no longer kept in the oil well but are forced into the pay zone andinto the fractures formed therein.

In another specific embodiment of the apparatus according to theinvention there is at least one turbine mixing device in the innertubing below the openings in the tubing, wherein the turbine mixingdevice comprises a shaft being supported by means of at least one plainbearing and carrying turbine vanes and mixing vanes. The plain bearingadditionally comprises openings allowing the passage of the fluidsflowing through the inner tubing. Further, the turbine vanes transmitenergy from the flowing fluids to the shaft to rotate the shaft with theattached mixing vanes and thus to mix the fluids. With such turbinemixing device the mixing can be improved compared to the above describedslot jet nozzles.

In the apparatus according to the present invention the mixing devicemay further be embodied by the lower end of the inner tubing beinglocated above the lower end of the outer tubing; and by at least oneturbine mixing device being arranged in the outer tubing below the lowerend of the inner tubing, wherein the turbine mixing device comprises ashaft being supported by means of at least one plain bearing andcarrying turbine vanes and mixing vanes. Additionally, the plain bearingcomprises openings allowing the passage of the fluids flowing throughthe inner tubing. The turbine vanes transmit energy from the flowingfluids to the shaft to rotate the shaft with the attached mixing vanesso that the fluids are mixed.

For stable support of the shaft the above described turbine mixingdevices comprise preferably two plain bearings.

In case more than one turbine mixing device is arranged in the apparatusdescribed above the mixing can be further improved if consecutiveturbine mixing devices have opposite directions of rotation.

The mixing device for the apparatus according to the present inventionmay alternatively be embodied by the lower end of the inner tubing beinglocated above the lower end of the outer tubing; and by a beakerinserted in the lower end of the inner tubing, wherein the beakercomprises openings in its bottom allowing the passage of the fluidssupplied through the inner tubing except the granular material suppliedwith the RIS.

As already mentioned above, the beaker can be made of aluminum or analuminum/magnesium alloy.

An alternative embodiment for an apparatus according to the presentinvention comprises:

-   -   a tubing inserted in a casing of the oil well such that an        annular space between the outside of the tubing and the inside        of the casing is provided, wherein a lower end of the tubing is        located in or above the pay zone of the oil well;    -   a packer being positioned above the lower end of the tubing and        sealing the annular space;    -   a beaker inserted in the lower end of the tubing, the beaker        comprises openings in its bottom allowing the passage of the        TGEC and RIS but not of granular material supplied with the RIS        through the tubing.

This beaker can also be made of aluminum or an aluminum/magnesium alloy.

With such apparatus a separate supply of TGEC and RIS is achieved bypumping the fluids in the form of fluid layers through the tubing. Toavoid mixing and reaction of the TGEC and RIS layers before reaching thepay zone a layer of a spacer fluid is arranged between the layers ofTGEC and RIS.

In the alternative apparatus described above the packer may comprisesensing elements for measuring the temperature of the packer and thepressure under the packer. This allows for better control of thethermochemical treatment process.

The alternative apparatus described above may further comprise at leastone reaction chamber in which the TGEC and RIS are reacted.

With respect to the apparatus and methods of the present inventionpreferred embodiments are described in the following, wherein referencesto the enclosed figures are made.

FIG. 1 shows an apparatus according to a first preferred embodiment ofthe invention.

FIG. 2 shows an apparatus according to a second preferred embodiment ofthe invention.

FIG. 3 shows an apparatus according to a third preferred embodiment ofthe invention.

FIG. 4 shows an apparatus according to a fourth preferred embodiment ofthe invention.

FIG. 5 shows an apparatus according to a fifth preferred embodiment ofthe invention.

FIG. 6 shows an apparatus according to a sixth preferred embodiment ofthe invention.

APPARATUS ACCORDING TO THE INVENTION

Following describes apparatus for thermally treating an oil reservoir byseparately introducing the thermal gas emitting composition (TGEC) andthe reaction initiator stabilizer (RIS) of the above described chemicalsystem in an oil well of the oil reservoir.

The apparatus according to the present invention for performing suchthermochemical treatment comprises:

-   -   an outer tubing inserted in a casing of the oil well such that        an outer annular space between the outside of the outer tubing        and the inside of the casing is provided,    -   wherein the lower end of the outer tubing is located in or above        the pay zone of the oil well;    -   a packer being positioned above the lower end of the outer        tubing and sealing the outer annular space;    -   an inner tubing inserted in the outer tubing, such that an inner        annular space between the outside of the inner tubing and the        inside of the outer tubing is provided, wherein the inner tubing        allows the supply of one of the TGEC or RIS to the pay zone and        the inner annular space allows the supply of the other one of        the TGEC or RIS to the pay zone, and wherein the lower end of        the inner tubing is located in or above the pay zone;    -   wherein at least one of the lower end of the outer tubing and        the lower end of the inner tubing is located in the pay zone of        the oil well; and    -   a mixing device contacting the TGEC and the RIS in the pay zone        of the oil well.

With this apparatus it is possible to separately supply the TGEC and theRIS through the oil well to the pay zone where the two compositions aremixed by means of a mixing device.

The mixing device of the apparatus further comprises at least onereaction chamber in which the TGEC and RIS are reacted.

The mixing device may be embodied by a sealed lower end of the outertubing being located above the lower end of the inner tubing and belowthe packer and by openings in the inner tubing allowing a fluid exchangebetween the inner annular space and the inner tubing. These openings arelocated at a distal section of the inner tubing but above the lower endof the outer tubing.

One of the factors affecting the efficiency of the method for thermallytreating an oil reservoir is the speed of heat production which dependson the mixing speed of the reagents and on their contact time in areaction chamber. The contact time can be extended by increasing thelength of the tubing below the openings. The tubing section below theopenings is designated as a reaction chamber or reactor.

For embodiments where granules of aluminum or an aluminum/magnesiumalloy are retained in a tubing (by means of a beaker with a perforatedbottom, as will be described later) the part of the tubing filled withthe granules can be designated as the reaction chamber or reactor.

Further, in case such granules of aluminum or an aluminum/magnesiumalloy are deposited in fractures in the productive layer also thevolumes of such fractures may be designated as a reaction chamber orreactor.

Different factors like the structure of the productive layer to betreated, the compositions of oil and natural gas in this productivelayer, the oil well design, and, in particular, how far the packer isplaced above the productive layer have an influence on what specificembodiment of an apparatus or a method according to the invention isbest for an effective thermochemical treatment of the productive layer.

For instance, the packer cannot be placed to far from the heatedproductive layer, yet the packer at the same time cannot be heated up tomuch.

Therefore, different embodiments of an apparatus and a method forthermally treating an oil reservoir will be described in the following.

For instance, the apparatus according to a first and second embodimentcomprise no movable parts and are thus most reliable. The apparatusaccording to a first embodiment, however, can be applied only incombination with a reaction chamber having a length of no less than80-100 meters. At a length of only 10-15 m, the efficiency index of suchapparatus is small.

If it is necessary to restrict the length of the reaction chamber toabout 10-15 m the apparatus according to the second, third and fourthembodiment can be used as the mixing devices used therein have a higherefficiency. In these embodiments no more than 10% of the chemical energysupplied with the TGEC and RIS is used for rotating a turbine mixingdevice and thus for mixing the fluids.

First Embodiment of an Apparatus

FIG. 1 shows a first embodiment of an apparatus for performing athermochemical treatment of an oil reservoir. An outer tubing (2) havinga diameter of about 2⅞ inch (7.30 cm) is inserted in a casing (1) of anoil well such that an outer annular space (7) between the outside of theouter tubing and the inside of the casing is provided. An inner tubing(3) having a diameter of about 1½ inch (3.81 cm) is inserted in theouter tubing (2), such that an inner annular space (8) between theoutside of the inner tubing and the inside of the outer tubing isprovided. The lower end of the inner tubing (not shown) is located inthe pay zone and the lower end of the outer tubing is located a givendistance above the lower end of the inner tubing and thus in or abovethe pay zone of the oil well. The lower end of the outer tubing issealed by attaching it to the outside of the inner tubing. Further, apacker (4) is positioned above the lower end of the outer tubing andseals the outer annular space so that no fluid can flow into the outerannular space (7). To avoid a thermal overload of the packer it ispreferred that the packer is located a sufficient distance in flowdirection of the supplied fluids before the first opening in the innertube. The packer may further comprise sensing elements for measuring thetemperature of the packer and the pressure under the packer.

The inner tubing allows the supply of one of the TGEC or RIS to the payzone and the inner annular space and allows the supply of the other oneof the TGEC or RIS to the pay zone. At a distal section of the innertubing but above the lower end of the outer tubing are provided fourslot jet nozzles. These slot jet nozzles are embodied by tubularconnecting passages (5) extending diagonal through the inner tubing andcomprising a slot (6). By means of these slot jet nozzles the fluidsupplied through the inner annular space flows into the tubularconnecting passages and through the slot (6) so that it is distributedin and thus mixed with the fluid supplied through the inner tubing. Itis of course possible to provide more than four slot jet nozzles. For abetter mixing effect the slot jet nozzles can be arranged such that twoadjacent slot jet nozzles are axially offset by a given angle. It isfurther preferred that the slots are formed in a lower half of thetubular connecting passages. In the preferred embodiment of FIG. 1 theslot jet nozzles are axially offset by 45° and the slots are formed atthe lowest point of the tubular connecting passages, i.e. in flowdirection of the fluid supplied through the inner tubing. The resultingstaggered arrangement of the slot jet nozzles as a view from the lowerend of the inner tubing is shown in the lower part of FIG. 1.

In this apparatus it is preferred to supply the TGEC through the innertubing and to supply the RIS through the inner annular space.

The length of the inner tubing below the lowest opening (slot jetnozzle) forms a reaction chamber in which the mixed TGEC and RIS reactunder production of heat and gases. The reaction chamber may have alength of up to 100 m or more and allow the reaction of up to 15 tons ofreagents per hour with a high reaction efficiency of approximately 90%.That is, approximately 90% of the energy obtained by reacting all thematerials supplied to the reaction chamber will be available forthermochemically treating the oil reservoir. The heated reactionproducts enter in the oil reservoir and increase the pressure under thepacker so that new cracks or fractures are formed in the productivelayer.

The apparatus shown in FIG. 1 is preferably used in oil wells where thepacker is located at a distance of no more than 100 m from theproductive layer and is characterized in that it has a simple structurewithout any movable parts and that as a result of the long reactionchamber a high reaction efficiency is provided.

Second Embodiment of an Apparatus

In case the packer is located no more than 10-15 m above the productivelayer it is preferred to use an apparatus according to a secondembodiment shown in FIG. 2. The apparatus according to the secondembodiment comprises a beaker (10) being inserted in the inner tubingbelow the lowest opening in the inner tubing. The beaker comprisesopenings in its bottom allowing the passage of the mixed fluids and hasa length of up to 4 m, preferably 3-4 m.

The openings in the bottom of the beaker (10) have such dimensions thatgranular material cannot pass and thus are kept in the beaker, so thatfor instance granules of aluminum or aluminum/magnesium alloy beingsupplied as a suspension through the inner tubing are retained in thebeaker as their particle diameter is larger than the diameter of theopenings in the bottom of the beaker.

The beaker may further be made from a material having a limited lifetimeduring the conditions of use. That is, the beaker is constructed suchthat after a calculated time of passing fluids through the beaker itsbottom breaks down so that the granular material retained therein isflushed into the productive layer. The beaker is preferably made ofaluminum or an aluminum/magnesium alloy which dissolves when contactedwith acidic or alkaline fluids or burns down in case of hightemperatures of about 700° C. or higher.

Third Embodiment of an Apparatus

The following describes a further embodiment of an apparatus forperforming thermochemical treatment of an oil reservoir. The presentembodiment comprises at least one turbine mixing device being arrangedin the inner tubing below the openings. The turbine mixing devicecomprises a shaft being supported by means of at least one plain bearingand carrying turbine vanes and mixing vanes, wherein the plain bearingcomprises openings allowing the passage of the flowing fluids andwherein the turbine vanes transmit energy from the flowing fluids to theshaft to rotate the shaft with the attached mixing vanes. The section ofthe inner tubing with a diameter of about 1½ inch (3.81 cm) below theturbine mixing device forms the reaction chamber of this apparatus. Thesection of the inner tubing between the first openings and the firstturbine mixing device can be designated as a pre-chamber. Approximately1/10 of the reagents react in this pre-chamber and the produced energyis at least partly used to drive the turbine mixing device(s) arrangeddownstream of the pre-chamber.

In FIG. 3 a specific embodiment of an apparatus according to a thirdembodiment is shown. In this specific embodiment the shaft (11) issupported by means of two plain bearings (12) comprising openings (15)allowing the passage of the flowing fluids. The shaft (12) carriesturbine vanes (13) and mixing vanes (14), wherein the turbine vanes arearranged prior to the mixing vanes with respect to the flow direction ofthe fluids. The turbine vanes transmit energy from the flowing fluids tothe shaft to rotate the shaft with the attached mixing vanes and therotated mixing vanes improve mixing of the TGEC and RIS. In the presentembodiment the mixing vanes (13) are perforated plates.

Fourth Embodiment of an Apparatus

The following describes an apparatus for performing thermochemicaltreatment of an oil reservoir according to a fourth preferredembodiment. The mixing device of the apparatus is embodied by the lowerend of the inner tubing (3) being located above the lower end of theouter tubing (2) and by at least one turbine mixing device beingarranged in the outer tubing below the lower end of the inner tubing.The turbine mixing device described above for the third embodiment canbe used.

If two or more turbine mixing devices are arranged it is preferred thatconsecutive turbine mixing devices have opposite directions of rotation.

A specific embodiment of such apparatus is shown in FIG. 4. It comprisestwo turbine mixing devices having opposite directions of rotation.Further, in this embodiment the outer tubing (2) is tapered between thelower end of the inner tubing (3) and the first turbine mixing device.

Like in the previous embodiment, the section of the inner tubing with adiameter of about 1½ inch (3.81 cm) below the turbine mixing devicesforms the reaction chamber of the present apparatus. The cone shapedsection of the outer tubing (2) can be designated as a pre-chamber.

Fifth Embodiment of an Apparatus

In FIG. 5 is shown a fifth embodiment of an apparatus for performingthermochemical treatment of an oil reservoir according to the presentinvention. The apparatus according to the fifth embodiment comprises noopenings in the inner tubing which allow a fluid exchange with the innerannular space (8). In the apparatus according to the fifth embodimentthe mixing device is embodied by the lower end of the inner tubing (3)being located above the lower end of the outer tubing (2) and by abeaker (10) inserted in the lower end of the inner tubing. This beakercomprises openings in its bottom allowing the passage of the fluidssupplied through the inner tubing except the granular aluminum material(16) supplied with the RIS. That is, when granules of aluminum oraluminum/magnesium alloy are supplied as a suspension through the innertubing the granules are retained in the beaker as their particlediameter is larger than the diameter of the openings in the bottom ofthe beaker.

The section of the inner tubing filled with the granules can be regardedas a first reaction chamber. The heat produced in this reaction chamberheats up the fluid (TGEC) pumped through the inner annular space (8) sothat the TGEC is ignited without the use of any further RIS. The sectionof the outer tubing below the lower end of the inner tubing can beregarded as a second reaction chamber.

If the apparatus according to the fifth embodiment is used with themethod of the third embodiment high temperatures of up to about 600-700°C. are achieved in the first reaction chamber so that the beaker shouldbe made from heat-resistant material.

However, if this apparatus is used for the hydrocracking method (fourthembodiment of a method) a beaker (10) of the same type as describedabove for the embodiment 2 can be used. Hence it is preferred that thisbeaker is made of aluminum or an aluminum/magnesium alloy.

Sixth Embodiment of an Apparatus

A sixth embodiment of an apparatus for performing thermochemicaltreatment of an oil reservoir according to the present invention isshown in FIG. 6. The apparatus comprises only one tubing (22) with adiameter of about 2⅞ inch (7.30 cm) inserted in the oil well. Thistubing (22) is inserted in the casing (21) of the oil well such that anannular space (25) between the outside of the tubing (22) and the insideof the casing (21) is provided, wherein a lower end of the tubing (22)is located in or above the pay zone of the oil well. A packer (24)sealing the annular space (25) is positioned above the lower end of thetubing (22). A beaker (23) is inserted in the lower end of the tubing,wherein the beaker comprises openings in its bottom allowing the passageof the TGEC and RIS but not of granular material supplied with the RISthrough the tubing.

The same type of beaker as described above for the embodiment 2 can beused. In that case, it is preferred that the beaker is made of aluminumor an aluminum/magnesium alloy. In that case, it is intended that thebeaker does not disintegrate during use of the apparatus the beaker ismade of a material having sufficient resistance under the thermal andchemical conditions present in the oil well during a method ofthermochemical treatment.

The apparatus according to the sixth embodiment is used by pumping TGEC(26) and RIS (27) in forms of layers being separated by a layer of aninert fluid or spacer fluid (28).

The section of the tubing filled with the granular material forms thereaction chamber of the present apparatus.

It should be generally noted that in the above described apparatusaccording to the present invention comprising a beaker for keeping RISgranules the beaker may be designed differently to fulfill therequirements of the method of thermochemical treatment for which theapparatus is used. For instance, the lifetime of the beaker under thechemical and thermal conditions in the oil well can be adjusted by usinga more or less resistant material or by adapting the thickness of thebottom of the beaker. If it is intended that the beaker does notdisintegrate during the thermochemical treatment it is prepared of arespectively resistant material.

METHODS ACCORDING TO THE INVENTION First Embodiment of a Method

In a first embodiment of a method of thermally treating an oil reservoirthe apparatus shown in FIG. 1, 3 or 4 can be used wherein it ispreferred to supply the TGEC through the inner tubing and to supply theRIS through the inner annular space wherein both compositions aresupplied as pumpable solutions or suspensions.

Second Embodiment of a Method

In a second embodiment of a method of thermally treating an oilreservoir the apparatus according to the second embodiment as depictedin FIG. 2 is used wherein the RIS is supplied through the inner tubing(3) and the TGEC is supplied through the inner annular space (8). As theRIS granular aluminum or aluminum alloy with magnesium is used thegranular material is supplied in the form of a suspension. The openingsin the bottom of the beaker (10) have such dimensions that the granularmaterial cannot pass and thus are kept in the beaker. For thisembodiment the amount of TGEC used is about 2-3 times the amount ofaluminum wherein this ratio refers to the mass of the reagents as suchwithout the solvent(s) used to prepare the pumpable solutions orsuspensions. As a preferred TGEC compound the reaction product ofreacting urea with nitric acid, i.e. urea nitric acid adduct, is used.With this embodiment up to 3 tons of reagents can be reacted per hour.The hot reaction products resulting from the reaction of the aluminum oraluminum/magnesium alloy comprise gaseous hydrogen. The pH value mayrange from 3 to 14, however, a pH of 3-4 is preferred as then theproduced hydrogen can be oxidized thus increasing the amount of producedheat by about 30%. With this method of thermochemical treatment a highpressure under the packer is achieved so that new fractures are createdin the productive layer.

This second embodiment of a method can be modified by shifting thereaction into the fractures of the productive layer as described belowin the fifth embodiment of a method.

Third Embodiment of a Method

For this method the apparatus according to the fifth embodiment can beused. First, a suspension of granular aluminum or aluminum/magnesiumalloy is pumped as a suspension into the inner tubing (3) so that at thelower end of the inner tubing where a heat-resistant beaker (10) isinserted the granular material is retained to form a layer (16) ofgranular material with a height up to about 200-300 m. Then a first TGECis pumped into the inner tubing so that reactions are initiated andthermal energy is produced in the first reaction chamber. In this methodhot gases with a temperature of up to 600-700° C. can be produced. Theheat produced in the first reaction chamber heats up the walls of thefirst reaction chamber, that is the distal end of the inner tubing, andthus the fluid (second TGEC) pumped through the inner annular space (8)so that the TGEC is ignited without the use of any further RIS. Theignited TGEC flows through the second reaction chamber, i.e. the distalsection of the outer tubing (2) below the beaker, where the TGEC reactsunder production of heat and gases.

Fourth Embodiment of a Method

A specific method of thermally treating an oil reservoir uses theprocess of hydrocracking of the petroleum in the oil reservoir. Underhigh temperature and pressure and the presence of gaseous hydrogencomplex hydrocarbon molecules are broken down to simpler hydrocarbonmolecules.

For this method the specific embodiments of an apparatus according tothe invention as shown in FIG. 2 and FIG. 5 can be used. Both apparatusare characterized in that they comprise a beaker at the lower end of theinner tubing which can retain and keep granules of aluminum or itsalloys with magnesium supplied with the RIS. For this method the beakeris also made of aluminum.

At the beginning a suspension of granules of aluminum or analuminum/magnesium alloy as part of the RIS is supplied through theinner tubing to the aluminum beaker. There it is contacted with the TGECsupplied through the inner annular space (second embodiment shown inFIG. 2) or the inner tubing (fifth embodiment shown in FIG. 5) whereinthe TGEC has preferably a pH value of about 3 or 14 so that hydrogen isevolved. The hot reaction products enter into the oil reservoir, heat upthe productive layer and increase the pressure under the packer so thatnew fractures are formed in the productive layer. Like in the secondembodiment of a method urea nitric acid adduct is preferably used as aTGEC compound and in an amount of about 2-3 times the amount of aluminumused.

Further, if a pH of 3-4 is used the produced hydrogen gas can beoxidized thus increasing the amount of produced heat.

After the increase of temperature and pressure and the formation offractures in the productive layer the reaction zone is shifted from theoil well into the productive layer. This is achieved by an alloweddisintegration of the aluminum beaker resulting from the acidic oralkaline conditions. That is, after about 10-30 minutes of pumping asolution with a pH value of about 3 or 14 through the beaker the bottomof the beaker breaks down and the granules are forced into the fracturesof the productive layer.

This reaction zone shift is preferably performed after the vicinity ofthe fractures has reached a temperature of about 300° C. This shiftingfurther reduces the thermal load of the packer and the tubings as thesupplied fuels now can cool down the packer and the tubings.

As a result of this shifting the temperature of the productive layer isfurther increased as now the reaction of aluminum or its alloys withmagnesium with the acidic or alkaline TGEC solutions takes place in thefractures. This results in temperatures of up to 400-500° C., a furtherincreased pressure and the presence of hydrogen. As above temperaturesof 300-350° C. the hydrocracking process starts the petroleum in theproductive layer now undergoes hydrocracking to smaller molecules sothat the viscosity of the petroleum is reduced.

The hydrocracking process may be further improved by supplyingcatalytically active compounds to the place of reaction. As suchcatalysts the above mentioned soluble metal salts of Mn, Fe, Cr, Co, Nior V may be used which can be added to the RIS or TGEC. With respect tothe total mass of the RIS such metal salts may be contained in the RISin an amount of not more than 10% by mass.

Especially preferred metal salts are Fe(NO₃)₃, Mn(NO₃)₂.6H₂O,Mn(SO₄).6H₂O, KMnO₄, K₂MnO₄, K₂CrO₄, Na₂CrO₄, K₂Cr₂O₇, Na₂Cr₂O₇,Co(NO₃)₃, NH₄VO₃, NaVO₃ and KVO₃.

During the process of hydrocracking of the petroleum the injection ofany oxidizing compounds into the layer should be avoided so that theproduced hydrogen is spent for the hydrocracking process only.

After the granules of aluminum or its alloys with magnesium areexhausted the layer can be heated up again by supplying TGEC and RIS andthe hydrocracking process can be initiated by supplying the next portionof granules. This leads to a cyclic reaction control of increasing heatand pressure in the productive layer and of performing the hydrocrackingprocess.

This hydrocracking process results in a considerably reduced viscosityof the petroleum in the treated oil reservoir as in addition to theincreased temperature in the pay zone the more complex hydrocarbonmolecules are broken down to simpler hydrocarbon molecules.

A further beneficial effect of the use of the aluminum oraluminum/magnesium alloys in this process is the reduction of the amountof water present in the oil well. During reaction of the aluminum oraluminum/magnesium alloy under alkaline conditions water is consumed.Further, the metal hydroxides resulting from the reaction of aluminum oraluminum/magnesium alloys have the characteristic of adsorbing orbonding water like in the form of water of crystallization. Theseeffects can be used to reduce the amount of water in oil wells beingcontaminated or damaged by too high contents of water.

During this thermochemical treatment of the oil reservoir the producedgases dissolve in the petroleum and thus further reduce the viscosity ofthe petroleum.

It should be generally noted that the substances used for the TGEC startto decompose and to evolve heat and gases if they are heated above about200-300° C. Hence, if it is mentioned in the present application thatTGEC and RIS are supplied to heat up a certain region, this alsocomprises the supply of only TGEC if this region already has atemperature at which the supplied TGEC will decompose to emit energy.

In this method an apparatus according to the invention as shown in FIG.2 and FIG. 5 can be used in combination with such chemicals as ammoniumnitrate, potassium nitrate, sodium nitrate and/or calcium nitrate, ureanitric acid adduct and the RIS compounds number 1 to 4 as designated inthe table presented previously.

Fifth Embodiment of a Method

A fifth method of thermally treating an oil reservoir by using the TGECand RIS mentioned above is characterized in that an apparatus can beused comprising only one tubing inserted into the oil well. Suchapparatus is exemplarily depicted in FIG. 6 and described above as asixth embodiment of an apparatus for performing thermochemical treatmentof an oil reservoir.

With such method and apparatus a separate but continuous supply of TGECand RIS is achieved by pumping the fluids in the form of fluid layersthrough the tubing. To avoid mixing and reaction of the TGEC and RISlayers before reaching the pay zone a layer of a spacer fluid isarranged between the layers of TGEC and RIS. As a spacer fluid any fluidcan be used being inert regarding reactions with the TGEC and RIS. Suchspacer fluid may be chloroform, for instance. The thickness of thespacer fluid layer is about 20-30 m.

After supplying granules of aluminum or aluminum/magnesium alloy as asuspension to the beaker where the granular material is accumulated alayer of spacer fluid and a layer of TGEC (acidic or alkaline solution)is pumped into the tubing. A contact time between the TGEC and thegranular RIS material of about 200 s is sufficient to start and maintainreactions producing heat and gases to heat up the surrounding productivelayer and to produce fractures therein. Like in the method describedbefore, the beaker when made from aluminum will be destroyed after acalculated time and the reaction zone is shifted into the productivelayer so that the thermal energy can be further distributed in theproductive layer.

In this method the reaction chamber is formed by the tubing filled withthe granular material which may form a layer of up to 50-200 m. Becauseof this, this method is suitable only for oil wells where the packer islocated at least 200-300 m above the productive layer to be treated.

It should be generally noted that in the above described methods wheregranules of aluminum or aluminum/magnesium alloy are distributed in thefractures of the productive layer the fractures can be increased withrespect to their length and volume and the productive layer can befurther heated by supplying a strong oxidizing agent like potassiumdichromate K₂Cr₂O₇ to the aluminum granules deposited in the productivelayer. These strong oxidizing agents support the production of largeamounts of energy and of solid metal oxides like Al₂O₃ which function asproppants (propping agents) to hold the fractures open.

With these methods a hot layer fracturing method is provided. Incontrast to the known cold hydrofracturing method where in a first stepa liquid (frac fluid) is injected into the oil well under pressure tocreate fractures in the formation and in a second step hard granularmaterial such as sand (proppant) is pumped into the formed fractures thepresent hot layer fracturing method comprises three steps. In a firststep the pressure for forming new fractures is not produced by the pumpspumping the material into the oil well but by the reactions in the oilwell producing hot gases. In a second step the granules of aluminum oraluminum/magnesium alloy are pumped into the fractures. Then, in a thirdstep, TGEC is injected into the oil well and into the fracturescontaining the RIS granules so that hot gases are produced in thefractures. This results in heating up the surrounding area and informing of further fractures. In this third step a strong oxidizingagent like potassium dichromate K₂Cr₂O₇ can be additionally provided tothe RIS granules deposited in the fractures as already mentioned above.

With the apparatus and methods described above it becomes possible tocontinuously produce thermal energy and hot gases which heats up theproductive layer and thus allows an efficient extraction of even heavyoil and bitumen.

EXAMPLES Comparative Example

For this comparative example the oil well #24193 at the “Irkenneft” oilfield (Russia, Tatarstan) was selected. 1.2 t of ammonium nitrate in anaqueous solution with a concentration of about 50% by mass was injectedinto the oil well, wherein its decomposition was initiated by mixing itwith an aqueous solution of 0.3 of sodium nitrite (NaNO₂). Thetemperature in the bore opposite the productive layer before thetreatment was 66° C. The temperature in the bore (oil well #24193)opposite the productive layer after one hour of treatment was 126° C.The speed of petroleum extraction from the oil well #24193 before thetreatment was 0.78 tons per day and after the treatment 1.86 tons perday.

Example According to the Invention

An aqueous solution of 1.3 t of mono ethanol amine nitrate was injectedinto the oil well #21 at the Razumovsky oil field in the Saratov region.The injected solution had a concentration of about 76% by mass of monoethanol amine nitrate and 2% by mass of nitric acid. Its decompositionwas initiated with the presence of 0.012 t of sodium borohydride(NaBH₄). The temperature in the bore opposite the productive layerbefore the treatment was 86° C. The temperature in the bore (oil well#21) opposite the productive layer after two hours of treatment was 269°C. The speed of petroleum extraction from oil well #21 before thetreatment was 2.6 tons per day and after the treatment 12.3 tons perday.

The above comparative example and example according to the inventionclearly show that with the present invention a higher increase ofpetroleum extraction can be achieved (about 373% for the exampleaccording to the invention) as compared with the methods used so far(about 138% for the comparative example).

Finally, it should be noted that the present invention is not restrictedto the preferred embodiments described above and that alternativeembodiments within the ordinary skill of a person skilled in the art arecomprised.

What is claimed is:
 1. A method of thermally treating an oil reservoirby initiating a chemical reaction in a pay zone of said oil reservoir,using a chemical system comprising at least the following twocompositions: a thermal gas emitting composition (TGEC) being an aqueoussolution or suspension comprising at least one compound selected fromthe group consisting of hydrazine nitrate, 1,1-di C₂₋₆ alkyl hydrazinenitrates and 1,2-di C₂₋₆ alkyl hydrazine nitrates, guanidine nitrate,formamide nitric acid adduct, acetamide nitric acid adduct, acetonitrilenitric acid adduct, urea nitric acid adduct, ammonium nitrate, potassiumnitrate, sodium nitrate, calcium nitrate, mono, di and tri C₁₋₅ alkylamine nitrates, mono, di and tri C₁₋₅ alkanol amine nitrates, C₁₋₆alkylene diamine mono and dinitrates and poly C₁₋₅ alkylene polyaminepolynitrates; and a reaction initiator stabilizer (RIS) being a liquidsolution or suspension and comprising at least one compound selectedfrom the group consisting of: metal borohydrides MBH₄, wherein M is Li,Na or K; aminoboranes (R¹R²R³)N.BH3, wherein R¹, R² and R³ areindependently hydrogen or C₁₋₁₀ alkyl, or wherein R¹ is an aryl orpyridine with up to 10 carbon atoms and R² and R³ are hydrogen;dialkylaluminates MAlH₂R¹R², wherein M is Li, Na or K, and R¹ and R² areindependently C₁₋₁₀ alkyl; aminoalanes (R¹R²R³)N.AlH₃, wherein R¹, R²and R³ are independently hydrogen or C₁₋₁₀ alkyl; and aluminum oraluminum alloys with magnesium, wherein said thermal gas emittingcomposition (TGEC) and said reaction initiator stabilizer (RIS) areseparately introduced into said oil reservoir and are contacted in thepay zone of said oil reservoir to initiate a chemical reaction producingheat and gases, and wherein the TGEC is continuously introduced into theoil reservoir and the RIS is introduced simultaneously and in acontinuous or intermittent way into the oil reservoir and wherein saidmethod comprises the steps of: (a) introducing granules of aluminum oran aluminum/magnesium alloy as the RIS into an oil well of said oilreservoir and keeping said granules in a first reaction chamber locatedin the oil well; (b) introducing a first TGEC into the oil well so thatit contacts said granules kept in said first reaction chamber forinitiating and maintaining a thermochemical reaction producing thermalenergy and heating up the walls of said first reaction chamber; (c)introducing a second TGEC into the oil well such that it comes incontact with the heated walls of said first reaction chamber and isignited; (d) passing the ignited TGEC to a second reaction chamber wherethe TGEC reacts under production of heat and gases; (e) passing producedhot gases into the pay zone of the oil reservoir (f) shifting thethermochemical reaction into the pay zone of the oil reservoir byallowing said granules to enter into the pay zone; and (g) contactingthe granules in the pay zone with the second TGEC introduced into theoil well and wherein the granules in the pay zone are additionallycontacted with at least one oxidizing agent.
 2. The method of claim 1,wherein the introduction of the TGEC and the RIS is continued during thechemical reaction to maintain a continuous reaction.
 3. The method ofclaim 1, wherein the TGEC is a reaction product of reacting nitric acidwith a respective amino compound.
 4. The method of claim 1, wherein thepH of the TGEC is about 3 to
 14. 5. The method of claim 1, wherein theRIS is a solution or suspension in a solvent.
 6. The method of claim 5,wherein the solvent is water or an organic solvent selected from thegroup consisting of petrol, ligroin, white spirit, kerosene and naphtha.7. The method of claim 1, wherein the aluminum or aluminum alloys withmagnesium are dispersed, pyrophoric or granular.
 8. The method of claim1, wherein the TGEC or the RIS additionally contain at least one solublesalt selected from the group consisting of Mn, Fe, Cr, Co, Ni or V. 9.The method of claim 1, wherein the TGEC and RIS are pumped into the oilreservoir at a rate of about 4-8 liters per second.
 10. The method ofclaim 1, wherein said reaction chamber is located in or adjacent to thepay zone of the oil reservoir.
 11. The method of claim 1, wherein ureanitric acid adduct is used as the TGEC.
 12. The method of claim 1,wherein the pH value in the reaction chamber is about 3-4 and whereinhydrogen gas produced by the thermochemical reaction is oxidized by H₂O.13. The method of claim 1, wherein the thermochemical reaction and thusthe granules are shifted into fractures present in the pay zone.
 14. Themethod of claim 1, wherein the thermochemical reaction is shifted intothe pay zone after the pay zone is heated to about 300° C.
 15. Themethod of claim 1, wherein petroleum in the oil reservoir is subjectedto a hydrocracking process.
 16. The method of claim 1, wherein the TGECand RIS are introduced in the form of fluid layers separated by layersof a spacer fluid.
 17. The method according to claim 1, wherein the1,1-di C₂₋₆ alkyl hydrazine nitrate is 1,1-dimethyl hydrazine nitrate,the 1,2-di C₂₋₆ alkyl hydrazine nitrate is 1,2-dimethyl hydrazinenitrate, or both.
 18. The method according to claim 1, wherein theoxidizing agent is potassium dichromate K₂Cr₂O₇.